Conventionally, in information process systems which synchronize time, there are some arts which add an acquired time information to a time required for transferring the time information to obtain a time information with fewer errors (e.g., see Patent Document 1).
Further, in conventional seismological observation systems, there are some arts which transmit a future time with respect to the current time from a master seismometer to a slave seismometer in advance, and calibrate the current time of the slave seismometer by the transmitted future time in response to a subsequent clock signal (e.g., see Patent Document 2).